The invention herein generally relates to a miniature electroacoustic instrument and, in particular, a modular hearing-aid instrument.
Hearing instruments typically are custom-designed to suit the anatomical and audiological needs of an individual user. Because custom-made devices can be very costly, it is desirable to mass-produce a hearing instrument that is relatively inexpensive, readily adaptable to most users"" anatomical and audiological requirements, and inconspicuous and lightweight. In addition, in order to mass-produce hearing instruments it is important to obtain a high manufacturing yield.
There are significant challenges associated with the development of mass-produced hearing instruments. Although the structure of the external auditory canal generally is a sinuous, oval cylinder with three sections, it varies significantly depending on the particular individual. Traversing the canal towards the tympanic membrane, the first section is directed inward, forward, and slightly upward. The next section tends to pass inward and backward. The final section is carried inward, forward, and slightly downward. The outer portion of the ear canal is surrounded by cartilaginous tissue, with the inner portion being surrounded by bone. The canal is lined by a very thin lining of skin, which is extremely sensitive to the presence foreign objects. Further details of the path and contours of the external auditory canal are described in U.S. Pat. No. 4,870,688, issued to Barry Voroba et al., and in U.S. Pat. No. 5,701,348, issued to Adnan Shennib, both of which are incorporated herein by reference.
U.S. Pat. 4,870,688 describes an in-the-canal miniaturized hearing-aid contained within a prefabricated earshell assembly composed of a hollow rigid body with a soft, resilient covering fixed to its exterior. The microphone, receiver, amplifier, and battery are all wholly contained within a prefabricated modular sound assembly which snaps into a patient-selectable prefabricated earshell assembly. The soft, resilient covering that is affixed to the exterior of the rigid core is intended to allow the cylindrical or elliptical shape of the in-the-canal hearing-aid to more easily conform to the individual variations in a user""s auditory canal.
U.S. Pat. No. 5,701,348 describes a hearing device having highly articulated, non-contiguous parts including a receiver module for delivering acoustic signals, a main module containing all of the hearing-aid components except the receiver, and a connector that is articulated with both the receiver module and the main module to permit independent movement of the receiver and main modules. Separation of the receiver from the main module, and the receiver""s articulation with respect to the main module, is intended to provide at least two degrees of freedom in movement and independent movement of the receiver module with respect to the main module, and vice versa.
Attempts have also been made to provide inserts intended to be used as a part of a hearing-aid device. U.S. Pat. No. 2,487,038, issued to Jasper Baum, describes an ear insert shaped for insertion into the concha or the outer cavity of an ear. It includes a series of ball-shaped ball-like wall sections each made with sufficiently thick walls so as to give them great stiffness and prevent substantial distortion of the cross-section of the sound-passage portions extending therethrough under the action of external bending forces when the insert is inserted into the curved space of the outer ear cavity. The ball-like wall sections are interconnected by short neck-like sections to readily flex and take up substantially the entire deformation to which the channel insert is subjected. Thin flexible, skirt-like protrusions project in outward and rearward directions from the ball-like wall sections to become wedged against the surrounding surface portions of the outer ear cavity for automatically establishing therewith an acoustic seal.
U.S. Pat. No. 3,080,011, issued to John D. Henderson, describes an ear canal insert with a very soft tip with mushroom-shaped flanges. A flexible mounting tube is considerably stiffer than the material of which the mushroom-shaped head portion flanges are formed so that it can be used to force the insert portion of the device into the ear canal.
U.S. Pat. No. 5,201,007, issued to Gary L. Ward et al., describes earmolds that convey amplified sound from the hearing-aid to the ear. An acoustic conduction tube extends into the ear canal and a flanged tip on the conduction tube creates a resonant cavity between the tip and the tympanic membrane. The tip is constructed of a flexible material to form a sealed cavity adjacent the tympanic membrane.
Despite numerous attempts including those described above, there remains a need for a mass-produced hearing instrument that is relatively inexpensive, readily adaptable to an individual""s atomical and audiological requirements, and that is inconspicuous and lightweight.
Cost is a major consideration in the development of mass-produced hearing instruments. It has been discovered that, of all the components in a hearing instrument, the microphone and receiver (loudspeaker) are generally the most costly. Of these components, the receiver is generally the more costly item. Accordingly, reduction of the cost of the receiver component can significantly lower the cost of manufacturing the hearing instrument. Many receivers are considered to be self contained in that they are mounted within their own metal housing. Generally, such receivers have small solder pads to which electrical connections are made. Such solder connections are sometimes fragile and have been known to break. During manufacturing of hearing instruments with such receivers, great care must be observed so as not to damage the receiver or the solder connections.
Further, cost may also be controlled by ensuring that a sufficient portion of hearing-aids produced function properly. If the manufacturing yield is low, and many hearing-aids fail to meet standards after final assembly, the cost benefits of mass-production may be annulled. Thus, significant savings may be made by designing hearing-aids which facilitate testing at various stages of production. Testing at various stages of production may help to dispose of defective parts before final assembly, thereby increasing the yield.
It has been recognized that the housings for shells used in conventional hearing instruments can become difficult and costly to manufacture. Their shapes are generally dictated primarily by the contours of the ear cavity in which they are intended to be positioned, but attempts to reduce the cost and difficulty of manufacturing conventional shells could reduce the available range of shapes and contours. Alternatively, the cost of manufacturing and the complexity of the manufacturing process remain substantial.
Batteries may serve as a power source for hearing-aids. As described in U.S. patent application Ser. No. 08/815,852, entitled xe2x80x9cDisposable Hearing Aidxe2x80x9d, some hearing-aids have the electronics of the device placed inside the battery chemistry. Because the battery cannot be replaced, the hearing-aid must be discarded when the battery energy is depleted. A target life for such a disposable hearing-aid may be 30 days. Most hearing-aids use replaceable batteries. The replaceable battery may be inserted into the hearing-aid, thereby providing the power source to operate the device.
Replaceable zinc-air batteries are commonly used to power hearing-aids. Prior to use, the battery is sealed with a pull-tab that prevents environmental effects, such as relative humidity and temperature, from affecting the shelf-life of the battery. The pull-tab also prevents air (hence oxygen) from entering the battery. To activate the battery, the pull-tab is removed and air (hence oxygen) is allowed into the battery. The battery is then inserted into the hearing-aid to provide the power source for operating the hearing-aid.
Metal-air cells, such as zinc-air or aluminum-air cells, use air to activate the cell. A typical air cathode may be composed of four primary components:
(1) A carbon matrix formed by activated carbon blended with an aqueous Teflon slurry, washed, dried, and pressed into a current collector; the carbon matrix may include a catalyst, usually a transition metal oxide;
(2) a nickel mesh which provides mechanical strength and serves as the current collector;
(3) a microporous, hydrophobic membrane, typically polytetrafluoroethylene; and
(4) an anode/cathode separator which prevents direct contact between the anode and cathode.
Zinc-air cells are activated when air, and in particular oxygen, is allowed to enter the cell. In some zinc-air cells, a pull-tab covers one or more small openings that allow air to reach the air-cathode assembly. The pull-tab may be designed to allow air to diffuse slowly into the cell. With the pull-tab sealing the cell, the cell is oxygen deprived and may not support the same current as an unsealed cell.
An electronic signal processing system for a hearing instrument includes two connectable sections: a microphone section and a battery section. The microphone section is shaped to enclose a microphone and signal processing circuitry. The bottom of the microphone section includes a plurality of conducting contacts. The battery section includes a casing for engaging the auditory canal and an integral battery. The top of the casing is patterned to electrically connect the integral battery with the plurality of conducting contacts at the bottom of the microphone section.
According to one aspect of the invention, the casing of the battery section has a wall accommodating an anode of the battery and a pair of signal leads. The signal leads extend from the top of the casing of the battery section to the bottom of the casing of the battery section. A receiver section shaped to enclose a receiver may be connected to the bottom of the battery section. The top of the receiver section is patterned to electrically connect the receiver with the pair of signal leads at the bottom of the casing of the battery section.
According to yet another aspect of the invention, a removable tab is positioned between the conducting contacts of the bottom of the microphone section and the top of the casing of the battery section. The removable tab substantially seals a vent in the battery casing. Oxygen is supplied to an electrode of the integral battery through the vent. The tab also prevents electrical contact between the integral battery and the plurality of conducting contacts at the top of the microphone section.
According to another aspect of the invention, a first plurality of conducting strips are formed on a top surface of the removable tab to facilitate testing of the microphone and said signal processing circuitry. A second plurality of conducting strips are formed on a bottom surface of the removable tab to facilitate testing of the integral battery.
According to yet another aspect of the invention, the receiver includes a plurality of receiver components which are mounted directly in the receiver section.
It is understood that the foregoing general description and the following detailed description are exemplary, but are not restrictive, of the invention.